Comtech EF Data VMS v3.12.x Vipersat - Manual (Page 246)

Network MN/22156, rev 12
4-28 VMS User Guide
As a result, each of the four AF service levels also have three Drop Precedence
levels for which the modem/router provides 12 separate queues.
An IP packet that best conforms to the flow criteria is assigned a Low drop
precedence, and thus has a higher probability of delivery during congestion than
a packet with a Medium (less conformance) or High (non-conformance) drop
precedence. The Low drop precedence level is preset to 100% of full to prevent
these packets from being dropped prior to the queue reaching its capacity.
Because the Low Drop Precedence Level is not editable, this parameter is not
displayed in the configuration dialog. Percentage full settings for the queue
depth are configurable for Medium and High Drop Precedence Levels.
Specify the Precedence Levels for Medium Drop (20-90, % full) and High
Drop (10-80, % full). Ensure that the setting for Medium is greater than the
setting for High.
Typically, DiffServ is implemented using exclusively Class Selector DSCP or
exclusively Expedited and Assured Forwarding DSCP. The Series800 class is
fully DiffServ compliant and will work with either DiffServ implementation or
with a combination of both.
Network | WAN | QoS | Groups
This menu item appears for CDM-800 units.
Selecting the Groups menu item opens the dialog for the QoS Groups listing
(figure 4-19).
Through the Group QoS feature, Variable Coding and Modulation (VCM) can
be implemented for the outbound carrier transmitted from the Hub to each of the
Remote sites. Configuration of this feature provides variable orders of
ModCods within the same carrier.
Lower-order ModCods can be assigned to meet the availability requirements of
those sites that have a lower EIRP:
• located on the outer area of the satellite footprint
• having higher incidence of rain fade
• using smaller antenna dish
Higher-order ModCods can be assigned to sites with a higher EIRP:
• located on the inner contours of the beam
• having lower incidence of rain fade
• using larger antenna dish
A QoS group is defined as a set of Remotes for which each has the same ability
to receive the Hub outbound carrier. This means that whenever a packet